In "A tutorial on ghost cancelling", W. Ciciora et al, IEEE Transactions on Consumer Electronics, Vol. 25, pages 9-44, 25. February 1979, the principle of ghost cancelling is described. A received test signal is compared with an ideal version of this test signal. The coefficients of a correction filter applied to the received test signal are adjusted in such a way that the filter output signal matches as much as possible to the ideal test signal. But the filter length is limited and in a lot of cases no sufficient ghost cancellation is possible.
In "Adaptive Noise Cancelling: Principles and Applications", B. Widrow et al, Proceedings of the IEEE, pages 1692-1716, Vol. 63, No. 12, December 1975, an LMS (least-mean-square) adaptive filter for noise cancelling is introduced, wherein a new filter coefficient w.sub.i(j+1) is calculated according to the formula EQU w.sub.i(j+1) =w.sub.ij +2*.mu.*.epsilon..sub.j *x.sub.ij,
where w.sub.ij is the respective existing coefficient, .mu. is a fixed adaptation constant, .epsilon..sub.j is the difference between the respective filter output y.sub.j and the corresponding value of the ideal reference signal and x.sub.ij is the respective value from the filter input signal.